The only means to sync content from Outlook 2011/2015 is via an Exchange Web Services server. MS disabled local synching in 2011 some time ago in an update timed with Apple's discontinuing Sync Services (iSync), and has not enabled any other means to sync, besides EWS, in the newer beta version of Outlook.
The only other means to sync Outlook to a Mac/iOS device is to manually drag events to a folder (like the Desktop) and import/export them from Apple Calendar.
People talk about Exchange Web Services as though it is the red-headed stepchild of Exchange access. That may have been the way it was. That is not the way it is.
My firm recently upgraded its Exchange server to
Exchange Server 2013. Our old Exchange Server allowed my Mac to access the server only through the
Outlook Web Access web client. On
Internet Explorer, the look-and-feel of
OWA nearly rivaled that of the Windows version of
Outlook. On all other browsers, OWA was very much the red-headed stepchild.
For reasons that baffle me, IT disabled access to the Exchange server outside the firm's LAN except by
OWA. The iOS Mail app had full access to the Exchange server, but only over Wi-Fi while on my firm's LAN. Because our old Exchange Server did not support EWS, I could not use
Outlook 2011 on my MacBook Pro or upgrade
Entourage 2008 to
Entourage EWS on my G5 running Tiger.
The upgrade to
Exchange Server 2013 has changed my world. Now all of my devices access Exchange Server via EWS. [My Windows 7 laptop does not, but this is not a deal breaker.] I see nothing that a Windows user on my firm's LAN can do that I can't do on any of my Macs or iOS devices. Under iOS, the Microsoft's iOS
Outlook app and Apple's
Mail app work equally well. I am now running
Entourage EWS under Tiger and
Outlook 2011 under Yosemite. I have full control on my Exchange account anywhere that I can access the Web.